The present invention relates to a disc drive slider microactuator and sensor, and more particularly to a silicon-based thin film electromagnetic transducer providing improved actuation force and sensor sensitivity in a disc drive system.
The density of concentric data tracks on magnetic discs continues to increase (that is, the radial distance between data tracks is decreasing), requiring greater precision of head positioning. Conventionally, head positioning is accomplished by operating an actuator arm with a large-scale actuator motor, such as a voice coil motor, to position a head on a gimbal at the end of the actuator arm. The large-scale motor lacks sufficient resolution to effectively accommodate high track-density discs. Thus, a high resolution head positioning mechanism, or microactuator, is necessary to accommodate the more densely spaced tracks.
Various microactuator locations and designs have been considered to achieve high resolution head positioning. One promising design involves inserting a silicon-based thin film structure between the suspension and the slider in a disc drive assembly. The microactuator includes, for example, an electromagnetic transducer having magnetic core materials forming a stator and a rotor, with conductive coils wrapped around the stator core in a solenoid-type or planar-type configuration. One of the major technical challenges in implementing such a microactuator is to provide sufficiently large actuation force to overcome friction forces and spring bias forces to drive the head at a speed high enough to accommodate the required bandwidth. Such a design must be realized in a relatively small wafer area, to keep costs reasonable and to allow easy integration into the disc drive design. It would also be useful for the microactuator to include a position sensor to discern the relative position of the movable portion of the microactuator.
Therefore, there is a need in the art for a microactuator design providing large actuation force with reasonable power consumption and within a reasonable wafer area to microposition a transducing head at a speed that accommodates the high bandwidth required by high performance disc drives, and further for a microactuator design that includes the capability to sense the position of the movable portion of the microactuator.
The present invention is a microactuator for positioning a transducing head over a selected track of a rotatable disc in a disc drive system having a flexure to support a slider carrying the transducing head. The microactuator includes a stator operatively attached to the flexure. The stator includes a first pole piece having first and second ends, and a second pole piece substantially parallel to and spaced from the first pole piece, also having first and second ends. A via magnetically connects the first pole piece and the second pole piece. The first and second pole pieces are shaped so that a first gap between the first end of the first pole piece and the first end of the second pole piece is smaller than a second gap between the second end of the first pole piece and the second end of the second pole piece. A plurality of coils are wrapped around the stator. The microactuator further includes a rotor confronting the second end of the first pole piece and the second end of the second pole piece, the rotor being operatively attached to the slider. The rotor is movable with respect to the stator in response to an electrical current applied through the coils, and movement of the rotor alters a radial position of the transducing head with respect to the flexure.
A further aspect of the invention is a dual port device for positioning and sensing the position of a transducing head with respect to a selected track of a rotatable disc in a disc drive system having a flexure to support a slider carrying the transducing head. First and second ports of the dual port device each include a stator operatively attached to the flexure. The stator includes first and second pole pieces substantially parallel to and spaced from each other and each having first and second ends. A via connects the first and second pole pieces. The first and second pole pieces are shaped so that a first gap between the first end of the first pole piece and the first end of the second pole piece is smaller than a second gap between the second end of the first pole piece and the second end of the second pole piece. A plurality of coils are wrapped around the stator. A rotor confronts the second end of the first pole piece and the second end of the second pole piece, and is operatively attached to the slider. The first port is a microactuator wherein the rotor is movable with respect to the stator in response to a current applied through the coils. Movement of the rotor alters a radial position of the transducing head with respect to the flexure. The second port is an inductive position sensor wherein movement of the rotor is related to an inductance of the sensor.
Another aspect of the present invention is a process of forming a microactuator for positioning a transducing head over a selected radial track of a rotatable disc in a disc drive system having a flexure to support a slider carrying the transducing head. A tub is etched in a substrate. A first insulating layer is deposited on the substrate. A bottom coil layer is plated on the first insulating layer at least partially in the tub. A second insulating layer is deposited on the bottom coil layer. A ferromagnetic core layer is formed on the second insulating layer. A third insulating layer is deposited on and around the ferromagnetic core layer. A top coil layer is plated on the third insulating layer to contact the bottom coil layer at a point spaced from the ferromagnetic core. A rotor is formed to confront the ferromagnetic core, the rotor being movable with respect to the ferromagnetic core.
A further aspect of the present invention is a process of forming a microactuator for positioning a transducing head over a selected radial track of a rotatable disc in a disc drive system having a flexure to support the slider carrying the transducing head. A bottom coil layer is plated on a first insulating layer, and a second insulating layer is deposited on the bottom coil layer. A yoke is formed on the first insulating layer. A ferromagnetic core layer is formed over the yoke. A third insulating layer is deposited on and around the ferromagnetic core layer. A top coil layer is plated on the third insulating layer to contact the bottom coil layer at a point spaced from the ferromagnetic core. A rotor is formed confronting the ferromagnetic core, the rotor being movable with respect to the ferromagnetic core. The rotor may also be formed over a yoke.
Another aspect of the present invention is a microactuator for positioning a transducing head over a selected track of a rotatable disc in a disc drive system having a flexure to support a slider carrying the transducing head. The microactuator includes a stator, a rotor and an air gap separating the stator from the rotor. The stator includes a bottom pole piece, a non-magnetic spacer on the bottom pole piece and a top pole piece vertically spaced from the bottom pole piece. The top pole piece includes a via portion connecting the top and bottom pole pieces. A plurality of coils are wound around the stator. The rotor includes a bottom pole piece, a non-magnetic spacer on the bottom pole piece and a top pole piece vertically spaced from the bottom pole piece. The top pole piece includes a via portion connecting the top and bottom pole pieces. The air gap separates the stator from the rotor such that the bottom pole piece of the rotor confronts the bottom pole piece of the stator, the non-magnetic spacer of the rotor confronts the non-magnetic spacer of the stator, and the top pole piece of the rotor confronts the top pole piece of the stator across the air gap.